Theoretical investigation of the superconducting pairing symmetry in a bilayer two-orbital model of pressurized La3Ni2O7.

Abstract

We investigate the superconducting pairing symmetry in pressurized La₃Ni₂O₇based on a bilayer two-orbital model. There are two symmetric bandsαandγ, as well as two antisymmetric onesβandδ. It is found that theγband induces considerable ferromagnetic spin fluctuation and prefers an odd-frequency,s-wave spin triplet pairing state. The addition of the other bands gradually enhances some antiferromagnetic spin fluctuations which eventually surpass the ferromagnetic one. The superconducting pairing then evolves from a spin triplet into ad-wave spin singlet, and finally into ans±-wave one. The competition between thed-wave ands±-wave pairings relies on the relative strength of the ferromagnetic spin fluctuation to the antiferromagnetic ones.